1. Field of the Invention
The present invention relates to a retaining structure for motor elements and, more particularly, to a retaining structure with a cap providing with a coupling portion and a stop for preventing at least one motor element from disengaging from an axial tube of the motor.
2. Description of Related Art
FIG. 1 of the drawings illustrates a conventional motor 1 comprising a base 11, a stator 12, a supporting member 13, a bearing 14, a positioning member 15, and a rotor 16. The base 11 includes an axial tube 111 for receiving the bearing 14. The stator 12 includes a winding 121. The supporting member 13 is fixed in an end of the axial tube 111 by force-fitting. An abrasion-resisting member 131 is mounted in a lower end of the supporting member 13. A restraining member 132 is placed on top of the supporting member 13 and includes a through-hole (not labeled) for retaining a shaft 161 of the rotor 16. The positioning member 15 is mounted on top of the bearing 14 to prevent the bearing 14 from moving relative to the axial tube 111 of the base 11, thereby assuring reliable assembly.
Still referring to FIG. 1, in assembly, the supporting member 13, the bearing 14, and the positioning member 15 are mounted into the axial tube 111 of the base 11 in sequence, with the supporting member 13 and the positioning member 15 respectively fixed in two ends of the axial tube 111 by force-fitting, thereby positioning the bearing 14 in the axial tube 111. The shaft 161 is rotatably extended through an axial hole (not labeled) formed by a through-hole in each of the bearing 14 and the positioning member 15 and a hole (not labeled) in the supporting member 13.
Still referring to FIG. 1, when the motor 1 turns, since the diameter of the through-hole of the retaining member 132 on top of the supporting member 13 is smaller than an end of the shaft 161 and since the retaining member 132 is engaged in a necked portion (not labeled) of the shaft 161, the rotor 16 is prevented from disengaging from the bearing 14. Further, the bearing 14 is prevented from moving in the axial tube 111, as the positioning member 15 is force-fitted in an end of the axial tube 111 of the base 11, with a bottom of the positioning member 15 pressing against a top of the bearing 14. Hence, the bearing 14 and the shaft 16 are reliably coupled to the base 11.
However, the above conventional bearing positioning structure for a motor has some drawbacks. First, the axial tube 111 easily deforms after a period of time due to heat expansion and cold shrinkage as well as stress generated during operation of the motor 1 such that the supporting member 13 and the positioning member 15 cannot be fixed in the axial tube 111. Hence, the bearing 14 is liable to disengage from the axial tube 111. Further, the dusts or impurities may enter the gap between the shaft 161 and the bearing 14 when the rotor 16 turns and creates air currents. The life of the motor 1 is thus shortened. Improvement in the bearing positioning structure for a motor is thus required.